Heart rhythm disorders are very common in the United States, and are significant causes of morbidity, lost days from work, and death. Heart rhythm disorders exist in many forms, of which the most complex and difficult to treat are atrial fibrillation (AF), ventricular tachycardia (VT) and ventricular fibrillation (VF). Other rhythms may be easier to treat, but may also be clinically significant including supraventricular tachycardia (SVT), atrial tachycardia (AT), atrial flutter (AFL), premature atrial complexes/beats (PAC, APC) and premature ventricular complexes/beats (PVC). Under certain conditions, rapid activation of the normal sinus node can even cause a heart rhythm disorder such as inappropriate sinus tachycardia or sinus node reentry.
Definitive diagnosis has often been performed using electrode-bearing catheters placed within the heart chambers. Electrodes have been positioned along a catheter shaft or basket splines in an attempt to analyze or map the electrical activity within a heart chamber. Mapping typically involves the use or formation external (patches on skin) of electrograms and internal (catheters with electrodes) electrograms. A typical electrocardiogram of the cardiac cycle (heartbeat) consists of a P wave, a QRS complex and a T wave. During normal atrial depolarization, the main electrical vector is directed from the SA node, and spreads from the right atrium to the left atrium. Atrial depolarization is represented by the P wave on the electrocardiogram. The QRS complex reflects the rapid depolarization of the right and left ventricles. The T wave represents the repolarization (or recovery) of the ventricles.
Devices of the prior art, however, often do not provide a complete and stable map of the electrical activity within a heart chamber (recording electrograms). In particular, electrical activity in certain portions of the right atrium and the left atrium (e.g. atrial septum, region of right pulmonary veins) are often difficult to map because of the inability of devices of the prior art to adequately conform to the irregular shape of the atria and their varying shapes during beating of the heart. Further, devices of the prior art do not provide dimensionally and/or spatially stable and complete electrograms as the prior art devices often move as the heart beats, thereby moving some or all of the electrodes away from the heart tissue and making the relative position of the electrodes variable to corresponding position of atrial tissue.
Thus, there is a need in the art for a cardiac mapping catheter that is capable of providing improved and dimensionally and/or spatially stable signals for diagnosis, and more complete coverage of the heart tissue, typically in the form of electrograms.